Ignition of fuel for lighting a well



June 21, 1960 o. G. KAAsA IGNITION 0F FUEL FOR LIGHTING A NELL .Filed Sept. 26. 1956 PRIMARY o2 cuNTNNmG GAS SECONDARY GAS G uw mm BT Ls 0 INVENTOR f. ORIN G. KAASA adn muml f. Wk (im,

ATTORNEY@ nited States arent IGNITION OF FUEL FOR LIGHTING A WELL Orin G. Kaasa, Tulsa, Okla., assigner to'Sinclair Oil 81 Gas Company, Tulsa, Okla., a corporation of Maine Filed Sept. 26, 1956, Ser. N0.. 612,143

16 Claims. (Cl. 166-438) This invention relates to the heating of underground formations, and, more particularly, the invention is concerned with a method for heating or lighting a subterranean stratum opposite a well bore through contact in the bore of water and a chemical substance reactive with water to provide a spontaneously 4ignitable reaction product in the vicinity of the stratum to be heated. This product is mixed with a. free-oXygen-containing gas and a hydrocarbon fuel to provide combustion. l

It has been proposed to heat underground formations for Various purposes usually associated with increasing recovery of oil by secondary recovery methods. For instance, heat may be applied in the immediate vicinity of a well bore to lower the viscosity of surrounding hydrocarbon materials. A more `important use of the heating lies in connection with in-situ combustion procedures. In a particularly advantageousmethod of this type, a fuel such as methane is combusted in an input well bore to heat the first few feet of adjacent petroliferous stratum to a temperature generally greater than about 400 F., eg. about 600 to 1200" F., to establish combustion in the stratum. This procedure is often referred to as well lighting. In one recovery method a cooling gas which will not support combustion can then be injected and as a resultv the heat front is moved into the formation away from .the input well bore. A free oxygen-containing-gas is subsequently injected to move the combustion front to `wards one or more output wells. By this method the hydrocarbon content of the formation is moved towards the output well, and substantially all of the oil can be :swept from the formation traversed by the combustion or .heat wave.

Usually in well heating or lighting procedures a burn- 'er device is lowered into the well to the vicinity of a bare formation which is to be heated or lighted. Aside `from having to provide an apparatus which satisfactorily mixes and burns air and fuel inthe well for initiating com- Ebustion in the stratum, considerable diiculty has been .experienced in .providing conditions conducive to the .initial heating of the fuel and oxygen-containing gas to combustion temperatures. Sometimes a sparking device is employed as a means for igniting a hydrocarbon fuel-air stream. Difficulties arise in these devices due to complications in burner structure and the fact that the Ioperator is several hundred feet from the level of burning. Depending upon the location and depth of the well, elevated pressures and temperatures may be encountered which affect the operation of the burner. Also electrical conductors must be employed and this gives rise to problems concerned with Stringing the conductors and proper construction as to wire sizes and electrical and thermal insulation. Needless to say, these various factors can be responsible for excessive costs and diiculties in operation, .particularly as the operator increases the distance the burner is projected into the well bore.

In the method of the present invention for heating or lighting `a subterranean Astratum many of the disadvantages of prior methods are avoided. In my method l contact in the vicinity of the stratum water and a chemical substance or material which reacts with the water to a-Eord a spontaneously combustible product. The water and reactive material are both conveyed in moving fluid streams to the location of contact. The reaction product is combusted in free oxygen supplied to the vicinity which in turn ignites a liquid or gaseous hydrocarbon fuel made available. In one embodiment, a suitable .reactive material, e.g. calcium phosphide, is added to the well bore" through a tubing carrying a free oxygen-containing gas and water is then immediately injected into the tubing so that the reactive material and Water will contact at or near the location of the Well stratum to be heated. The mixing of the water and reactive material provides a spon-l taneously ignitable product which combusts in oxygen proA employed during water injection is of a relatively lowV order. When the flow velocity is increased during the addition of the reactive material, I prefer that this Velocity be at least about twice that employed during the water injection. A particular advantage of my method lies in its ability to be used under diverse well conditions, for instance temperatures of about 50 to 350 F. or more and pressures from about atmospheric to 10,000 lbs. or more.

Perhaps the method of the present invention can be best described by reference to a particular operating procedure as illustrated in the drawing which is a diagram-v matical sketch of a well bore equipped with a useful tubing arrangement and a container at the top of the well for holding and introducing into the bore the material which is reactive with water to produce the spontaneously ignitable reaction product.

ln the embodiment of the drawing the well is 825 feetdeep to the top of the oil sand and a well head pressurel of 750 lbs. will force gas freely into the oil sand. A 2- inch steel tubing 1 is cemented at Z in a 6-inch bore with a mix from 60 sacks of cement, and the tubingextends down to the oil sand. Below the lower end of the tubing is a bore hole several feet in height. Inside of tubing l is placed a 3r-inch diameter steel tubing string 3 which reaches from near the oil sand through the well head 4 extending across tubing l. Primary air at 750 p.s.i.g. pressure and at the rate of 1000 cubic feet per hour (STP) enters the well through valved 'eli-inch diameter steel pipe S which goes into tubing 3 just above the well head 4. When natural gas is used, it is preferably about 5 to l5 volume percent of its mixture with the primary air. Gas which is essentially methane is supplied at 750 p.s.i.g. pressure and at the rate of cubic feet per hour (STP) through a valved 1z-inch steel line 6 entering tubing 1 just below the Well head 4. Line 6 continues down in the annulus between tubing strings l and 3 and enters tubing 3 a short distance, for instance 5 feet, from its lower end.

On the top of tubing 3 is a container 8 holding solid particulate commercial calcium phosphide (Baker and Adamson) which contains some calcium pyrophosphate. The solid particles are for the most part from s to Mz. inch at the largest diameter. The container is isolated from tubing 3 by valve 7 and can be lled by way of valved line 13. Entering line 5 isa valved 1At-inch steel line 9 through which water is `injected into the primary air. Secondary air under a pressure of 7 50 p.s.i.g. and at Patented .lune 21, 1960 :trate of 4000 cubic feet per holu' (STP) .is passed into valved Z-'i'nch steelmlirie'I I0 entering tubing l below the welll head 4.' Thermowell 11 is located at the lower end of tubing 3 to follow the temperatures during the lighting procedure `and it houses a thermocouple (not shown). 'The leads frmhe therniocouple pafssV through thernowell il tothe surfaceat 12.

f operation the primary air,fsecondary air and hydrocarbon fuel iiows are started in linesVA 5, Mend 6, respectively;` The valve y7 isthen opened to ,admitftotubinfi 3 allof the'300 grams of calcium phosphide container S'a'rd during'this admission the flow rateofprix-nary air through line is 3000 SIP) cubic feet perhour. lmrnediatelyA after thephosphide vis inject-led, valve i is closed,"the'ow rateline 5 is ,d'riplilbfkrV to 10.00 su iwbiic'pfef reir-Qa Las aan@ if .teef charged by )Ver 0f 1in@ 9 et 1.1%@ .fegf 7 gallons Per rrrinute. 'During .the-passage ofthe phosphide and water down theftubing a reaction ,between theseA materials is initiated and the resulting rniprture of Arnonoand diphosphine is combusted in the primary air in the lower end of tubing 3. This combustionthen initiates burning of substantially all of the hydrocarbon fuel and another portion of the fuel would be combusted when it contacts the secondary air if insuiiicient primary air is used. When the temperature reaches a steady state at the lower end of tubing 3 to indicate the combustion of the hydrocarbon fuel is well established, no further water and phosphide injections are required. lf desired, the `lower ends of tubings 1, 3 and 6 can be made of stainless Vsteel or other heat resisting metals.V

-Although my method has been described in conjunction with the system of the drawing, it can be effected in anumber `of other ways. As examples, the Water might b injected vwith the primary air and the phosphide with the hydrocarbon fuel or vice versa. If tubing sizes permit, the water and phosphide couldboth be injected with the fuel with the waterinjection following that of the phosph'ide as in the system ofthe drawing.

lIn the method of this invention the heating of the stratum'can be continued as long as desired, and the character of the combustion andthe temperature of the surrounding formation can be followed as by analysis of combustion gases taken from an adjacentl output well (notshown)'.f In well lighting procedures the heating will usually be continued until the' temperature Aof the adjacent stratum is inthe range of 400't'o l200 F.V for atleast a Z-foot radius around'the well bore so that upon supplying a vfree oxygen-containing gas' a' combustion wave'will bemairitained in the"fformation. The op- 'iator"*may- ,choose to provide extraneous fuel while propagating the heat wave andthe 'combustion wave in vmy method it is often advantageous that the reactive chemical be a solid comprised substantially of granularor macrosize particles, for instance having at least one dimensionl of not less than about 1/32 of an inch. Finely divided material,`e.g. phosphides, tend to stick toand react in the upper portions of the tubing. Also, the nely divided solid can plug the tubing and may have such a short reaction time that no substantial amount of spontaneously ignitable product will beimade available in 'therlower regions of the well where burning is usually described. The upper limit on particle size can vary considerably with a primary factor being that the particle'sfmust be able topass through the tubing. Preferably, macrosized solid in which substantiallyall of the particles-"have dimensions of not more than about 1/4 of ninch is employed.VV In the system of the drawing there liasbeen sorne indication that ,the solid phosphide particles, s tant reacting with the waterbefore they reach thc lower end' portion of the burner tubing so inorder to insurey'the production and combustion of thevpho'sphine, itis preferred that the particles have one dimension vof Generally, the amount of gaseous or liquid hydrocarbon fuel supplied to the well bore will be such that its mixture with'all of the oxygen-containing 4"'gas'available will have a heat of combustion of less than about 40 B.t.u.s per cubic foot. Accordingly, when employing air and a hydrocarbon gas of 1000 B.t.u. per cubic `foot quality, the latter is preferably not greater than about 4 volume percentofgtlfretotal air provided. With lower wB.t.u. hydrocarbon fffuels increased volumes of fuel caribe used to maintain* aheat of 'corribstionof about l5 to l0 B.t.u.s per cubic foot of `totahfttrel and air mixture. N'flhe gua plied will depend up o A A final gas mixture. 'Whetherthe secondary gas be inert, air or hydrocarbon'fuel,itserveszprimarily to reduce the temperature of the combustionpfdfcts," for ins-tance to avoid formation spalling and destruction of metal. It may be desirable to heat the well with a rich fuel-air m' yture,i.e. one in which Aj.h elarr1ou.t 1t ofoxygenwigs innu Toute wllierycle are. e011- taining free oxygen whichA might give 4risettonex Y Combustin in this case` yshould essentially `c my the burner bethe vcase where Ll Supply! far install@ 199.0' air, Ycubic feet'per zhourof B.t.4u. fuel. gas and; Cubic fef Per hour .0f hytcarbgn gf inert .Sages/Clary gas How .to provide a mixture ofombustionproducts and secondary sas; having .a fsmuerafuiebslow 190.0 .F Should it be desired to heatuthe stratum,throughy e` liner then the tud-,rich 4taastvtal mixture with Substantially free oxygen .could maintain temperatures WSillfi'rl@ for liner. use `witlmlt `incurring the. possibility of btandeleteriusly Yhigh temperatures due t0 the presence 0f carbon andvufree oxygen.

Although the method of .the .present invention has beendescribed mainly with referenceto the use of calciurnV phosphide, other materials which react with water to give a spontaneously ignitable product can be employed. A number of such materials areknown, e.g. sodium, potassium and the metal phosphides, particularly those of metals havingatomic numbersup to about 40. The various useful phosphides include those of the metals of Group I, such as sodium andlithium phosphides,and the Group II metal phosphides, for instance those of beryllium and magnesium. Aside from the alkali metal phosphides of Groups VI and II, among the kother metal phosphides which 'can be employed are those of aluminum and arsenic. These latter phosphides reactmoderately'fast with water to provide a phosphine-containingproduct but if desired the speed of 'these' reactions canbe enhanced bythe use of ignition promot'ers'such as nitric oxide; Such promoters'also can be employedwththe alkali metal phosphides; however, "they will usually not be required.

In the description of my method I have employed the term phosphine to designate both monophosphine and'diphosphine. As previously noted the mixture obtained through the reaction of calciumphos'phide and Water contains both monoand diphosphine, and, it'is believed that the latter is particularly eifectivetwards making the mixture spontaneously ignitable'in afree oxygen-containing gas at moderate temperatures, say'50 to` F., which exist in -a' great 'many Well bores. Monophosphine isv alsospontaneously ignitablein a' free oxygen-containing gas, but if diphosphine be not present, well bore temperatures of at least about F. are advantageous. I prefer,therefore',l togenerate in the Well borediphosphine 'or mixtures of mono-fand diphfsphin'e, and when'such mixturesa're provided the diphosphine can ignite at a low temperature to promote the combustion of the monophosphine.

It is claimed:

1 ,In a method for lighting and continuing combustion of a Ahydrocarbon fuelins'awell bore "penetratingai'subl terranean formation, the steps comprising introducing a moving liuid stream of hydrocarbon fuel into the well bore, introducing into the well bore a metal phosphide in a moving uid stream, introducing water into the well bore in amoving uid stream to provide contact between the metal phosphide and water to produce a spontaneously combustible reaction product in the vicinity of the desired location of lighting, contacting the spontaneously combustible reaction product with an oxygen-containing gas to provide combustion and said combustion serving to initiate and continue combustion of the hydrocarbon fuel.

2. The method of claim 1 in which both the metal phosphide and the water are introduced in one of the hydrocarbon fuel and oxygen-containing gas, the introduction of the water immediately following that of the metal phosphide.

3. The method of claim 1 in which there is supplied insufficient oxygen to provide combustion of al1 of the hydrocarbon fuel.

4. 'Ihe method of claim 1 in which a secondary gas is introduced into the bore to reduce the temperature of the combustion products.

5. The method of claim 1 wherein the metal of the metal phosphide has an atomic number up to about 40.

6. The method of claim 5 wherein the metal phosphide is calcium phosphide.

7. In a method for lighting and continuing combustion of a hydrocarbon fuel in a well bore penetrating a subterranean formation, the steps comprising introducing into said bore a hydrocarbon fuel, oxygen-containing gas and a moving stream of macrosized metal phosphide particles, capable of reacting with water to produce spontaneouslycombustible phosphine, with at least one of the hydrocarbon fuel and oxygen-containing gas, contacting the phosphide with water in the vicinity of a desired location of lighting to produce said phosphine, said oxygen-containing gas contacting said phosphine to provide combustion and said combustion serving to initiate and continue combustion of the hydrocarbon fuel in said oxygen-containing gas.

8. The method of claim 7 in which the contacting of and the water are introduced in one of the hydrocarbon fuel and oxygen-containing gas, the introduction of the water immediately following that of the phosphide.

10. The method or" claim '7 wherein the metal of the metal phosphide has an atomic number up to about 40.

11. The method of claim l0 wherein the metal phosphide is calcium phosphide.

12. In a method for lighting and continuing combustion of a hydrocarbon fuel in a well bore penetrating a subterranean formation, the steps comprising introducing into said bore through a iirst tubing an oxygen-containing gas stream, introducing hydrocarbon fuel through a second tubing in said bore which enters the first tubing near its lower end, introducing into said oxygen-containing gas stream, a stream of macrosize metal phosphide particles capable of reacting with water to produce a spontaneously combustible phosphine, and immediately thereafter reducing the rate of ow of the oxygen-containing gas stream and introducing water intro said oxygencontaining gas stream to produce the spontaneously combustible phosphine in the vicinity of a desired location of lighting, said phosphine combusting in said oxygen-containing gas stream, thereby initiating and continuing combustion of the hydrocarbon fuel.

13. The method of claim 12 in which a gas stream is injected into the bore around said rst tubing to reduce the temperature of the combustion products.

14. The method of claim 12 in which the contacting of the water and the phosphide produces a mixture of monoand diphosphine.

15. The method of claim 12 wherein the metal of the metal phosphide has an atomic number up to about 40.

16. The method of claim 15 wherein the metal phosphide is calcium phosphide.

References Cited in the file of this patent UNITED STATES PATENTS 797,529 Oliphant et al. Aug. 15, 1905 1,806,499 Ranney et al. May 19, 1931 1,870,320 Adams et a1 Aug. 9, 1932 2,747,672 Simm May 29, 1956 OTHER REFERENCES Jones: Inorganic Chemistry, published 1947, by Blakistone, pages 377 and 378. 

